WCP1687

[1]

Parkstone, Dorset

August 8th. 1892

Sir Archibald Geikie.F.R.S.

Dear Sir

I have just been reading with great interest & pleasure your address to the Brit[ish] Association as reported in "Nature". There is however one point on which, I think, your calculations as to Geological time require alteration. On p. 322. col[umn] I. par[agraph] 2, you assume that deposits are formed at the same average rate as denudation, and found your calculation upon it. But in my "Island Life" (1st. Ed[ition] pp 314-315 — 2nd Ed[ition] pp. 221-223) I have argued, and I can still see no flaw in that [2] argument, that deposition, as measured by the maximum thickness of the sedimentary rocks, would go on at about 20 times the rate of denudation. Perhaps, as I have no authority as a geologist, your attention has never been called to these passages, but the argument there given seems to me to be indisputable, and to offer an important means of harmonising[?] the estimates of geologists & physicists as [3] to the duration of geological time.

Should you accept the validity of my argument you will probably like to modify the position of your address before it is officially issued.

Believe me | Yours very faithfully | Alfred R. Wallace [signature]